The solitary pulmonary nodule (SPN) is a common and challenging problem, with approximately 150,000 new SPNs being detected each year. The most common etiology of SPN remains lung cancer. While progress has been made in reducing the occurrence of benign nodules among resected ones, it continues to be approximately 50 percent. Many approaches to preoperative determination of the nature of the SPN have been tried, including evaluation of different features such as spiculation, tumor-bronchi relationship, degree of contrast enhancement with CT and MRI, metabolic activity using positron emission tomography as well as clinical criteria such as age and smoking history. The only criteria widely accepted as reliable for classifying nodules are the pattern of calcification and lack of growth for two years. The pattern of calcification has been studied extensively using CT as it allows better density discrimination than chest radiography. This approach has met with limited success. Growth, however, defines the very nature of tumors. Although, CT scanning, with its current resolution of 0.3 mm, is excellent in measuring size, virtually no work has been done using it to detect growth. The objective of this proposal is to determine the usefulness of early repeat CT (ERCT) imaging of SPNs for early and rapid diagnosis of lung cancer. We plan to develop methods of determining whether the SPN is growing, and/or changing its configuration, and for quantifying these changes. Thereupon, we will assess the probability of malignancy of an SPN as to how this depends on the ERCT findings. Our techniques should allow determination within a short period of time, in some cases within weeks, of whether an SPN is suspicious for malignancy and to recommend the course of action, whether further diagnostics, surgery or follow-up.